Field of the invention:
The present invention relates to an improved process for the preparation of 7-cyclopentyl-N,N-dmiethyl-2-{[5-(piperazm-l-yl)pyridm-2-yl]arnino}-7H-pyrrolo [2,3-d]pyrimidine-6-carboxamide succinate (1/1) compound of formula-la and its 5 novel crystalline forms. The said compound of formula-la is represented by the
The present invention also involves the usage low cost reagents, solvents and the process conditions which can be easily adopted for commercial scale.
Background of the Invention:
The 7-cyclopentyl-N,N-dimethyl-2-{[5-(pipera2in-l-yl)pyridin-2-yl]amino}-7H-pyrrolo [2J3-d]pyrimidine-6-carboxamide succinate (1/1) is commonly known as Ribociclib succinate. Ribociclib succinate was developed by Novartis and Astex Pharmaceuticals which is an anticancer agent useful for the treatment of certain kinds of breast cancers. The trade name of Ribociclib succinate is Kisqali, dosage form is tablet.
US patent US9193732 (Applicant: Novartis AG and Astex Pharmaceuticals) disclosed two physical forms namely hydrate and non-hydrate forms of Ribociclib

succinate of formula-1 a. Ribociclib succinate was prepared by treating Ribociclib base of formula-1 with succinic acid in isopropyl alcohol. The resulting Ribociclib succinate was subjected to relative humidity 0-90-0% RH and 0-80-0% RH. Ribociclib succinate absorbs moisture up to 2.0% at 0-90-0% RH and up to 0.5% at 0-90-0% RH. Dynamic Vapour sorption (DVS), PXRD, DSC and Thermogravimetric analysis of these two hydrate and non-hydrate forms of Ribociclib succinate of formula-la were also discussed. However, when following the proposed route of synthesis the obtained Ribociclib has low yield and purity. Hence, there is a need in the art to develop an alternate and improved process for the preparation Ribociclib succinate which enhances the yield and purity of the desired compound.
Polymorphism, the occurrence of different crystal forms, is a property of some molecules and molecular complexes. A single molecule, may give rise to a variety of crystalline forms having distinct crystal structures and physical properties like melting point, X-ray diffraction pattern, infrared absorption fingerprint, and solid state NMR spectrum, thermogravimetric analysis ('TGA'), and differential scanning calorimetry ('DSC) which have been used to distinguish polymorphic forms.
The difference in the physical properties of different crystalline forms result from the orientation and intermolecular interactions of adjacent molecules or complexes in the bulk solid. Accordingly, polymorphs are distinct solids sharing the same molecular formula yet having distinct advantageous physical properties compared to other crystalline forms of the same compound or complex.
One of the most important physical properties of pharmaceutical compounds is their solubility in aqueous solution, particularly their solubility in the gastric juices of a patient. For example, where absorption through the gastrointestinal tract is slow, it is often desirable for a drug that is unstable to conditions in the patient's stomach or intestine to dissolve slowly so that it does not accumulate in a deleterious environment. Different crystalline forms or polymorphs of the same pharmaceutical compound can reportedly do have different aqueous solubility. Pharmaceutical compounds having different crystalline forms or polymorphs have different dissolution property. It

enlarges the repertoire of materials that a formulation scientist has available for designing, for example, a pharmaceutical dosage form of a drug with a targeted release profile or other desired characteristic features.
The discovery of new crystalline or polymorphic forms of a pharmaceutically useful compound provides a new opportunity to improve the performance characteristics of a pharmaceutical product.
Hence, there is a significant need in the art to develop novel polymorphs of Ribociclib succinate which are stable and also improves the performance characteristics of a pharmaceutical product.
The present inventors have developed novel crystalline forms of Ribociclib succinate and its process for preparation thereof.
Brief description of the Invention:
The first aspect of the present invention is to provide an improved process for the preparation of Ribociclib succinate compound of formula-la.
The second aspect of the present invention is to provide a novel crystalline form of Ribociclib succinate compound of formula-la hereinafter designated as "Form-A" and its process for the preparation thereof.
The third aspect of the present invention is to provide a novel crystalline form of Ribociclib succinate compound of formula-la hereinafter designated as "Form-B" and its process for the preparation thereof.
The fourth aspect of the present invention is to provide a novel crystalline form of Ribociclib succinate compound of formula-la hereinafter designated as "Form-C" and its process for the preparation thereof.
The fifth aspect of the present invention is to provide a novel crystalline form of Ribociclib succinate compound of formula-la hereinafter designated as "Form-D" and its process for the preparation thereof.
:FTTF r H F W N AT 9 3. /01/201S 12=44

The sixth aspect of the present invention is to provide a novel crystalline form of Ribociclib succinate compound of formula-la hereinafter designated as "Form-E" and its process for the preparation thereof.
The seventh aspect of the present invention is to provide a novel crystalline form of Ribociclib succinate compound of formula-1 a hereinafter designated as "Form-N" and its process for the preparation thereof.
Brief description of the Drawings:
FIG.l: Illustrates a characteristic PXRD pattern of crystalline Form-A of Ribociclib
succinate compound of formula-la.
FIG.2: Illustrates a characteristic PXRD pattern of crystalline Form-B of Ribociclib
succinate compound of formula-la.
FIG.3: Illustrates a characteristic PXRD pattern of crystalline Form-C of Ribociclib
succinate compound of formula-la.
FIG.4: Illustrates a characteristic PXRD pattern of crystalline Form-D of Ribociclib
succinate compound of formula-la.
FIG.5: Illustrates a characteristic PXRD pattern of crystalline Form-E of Ribociclib
succinate compound of formula-la.
FIG.6: Illustrates a characteristic PXRD pattern of crystalline Form-N of Ribociclib
succinate compound of formula-la.
FIG.7: Illustrates DSC thermogram of crystalline Form-N of Ribociclib succinate
compound of formula-la.
Advantages of the Invention:
• The present invention avoids the usage of expensive agents like HBTU, Tris(dibenzylideneacetone) dipalladium(O) (Pd2(dba)3), (+/-)-2,2'-Bis(diphenyl phosphino)-l,r-binaphthyl (BINAP).

• The present invention involves the usage of low cost reagents and solvents which decreases the cost of production and suitable for the commercial scale process.
• The process of the present invention provides Ribociclib succinate with high yield and purity.
Detailed description of the Invention:
The term "suitable solvent" used in the present invention refers to "hydrocarbon solvents" selected from aliphatic hydrocarbon solvents such as n-hexane, n-heptane, cyciohexane, petroleum ether and aromatic hydrocarbon solvents such as benzene, toluene, xylene and the like; "ether solvents" such as dimethyl ether, diisopropyl ether, diethyl ether, methyl tert-butyi ether, 1 ,2-dimethoxy ethane, tetrahydrofuran, 1,4-dioxane, monoglyme, diglyme and the like; "ester solvents" such as methyl acetate, ethyl acetate, isopropyl acetate, n-butyl acetate and the like; "polar-aprotic solvents such as dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone (NMP) and the like; "chloro solvents" such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride and the like; "ketone solvents" such as acetone, methyl ethyl ketone, methyl isobutyl ketone and the like; "nitrile solvents" such as acetonitrile, propionitrile, isobutyronitrile and the like; "alcoholic solvents" such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol and the like; "polar solvents" such as water or mixtures thereof.
As used herein the present invention, the term "anti-solvent" refers to a solvent which is used to precipitate the solid from a solution.
As used herein the present invention the term "suitable base" refers to "alkali metal carbonates" such as sodium carbonate, potassium carbonate, lithium carbonate and the like; "alkali metal bicarbonates" such as sodium bicarbonate, potassium bicarbonate and the like; "alkali metal hydroxides" such as sodium hydroxide, potassium hydroxide, lithium hydroxide and the like; "alkali metal alkoxides" such as sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide,

sodium tert.butoxide, potassium tert.butoxide, lithium tert.butoxide and the like; alkali
metal hydrides such as sodium hydride, potassium hydride, lithium hydride and the
like; alkali metal amides such as sodium amide, potassium amide, lithium amide and
the like; and organic bases like dimethyl amine, diethylamine, diisopropylamine,
5 diisopropylethylamine, diisobutylamine, triethylamine, pyridine, 4-
dimethylaminopyridine (DMAP), N-methyl morpholine (NMM), 2,6-lutidine, lithium
diisopropylamide; organosilicon bases such as lithium hexamethyldisilazide
(LiHMDS), sodium hexamethyldisilazide (NaHMDS), potassium
hexamethyldisilazide (KHMDS) or mixtures thereof.
10
The first aspect of the present invention is to provide an improved process for
the preparation of Ribociclib succinate compound of formula-la, comprising of:
a) Reacting 2-Chloro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic
acid compound of formula-2 with dimethylamine in presence of a suitable
15 coupling agent, suitable base in a suitable solvent to provide 2-chloro-7-
cyclopentyl-N]N-dimethyl-pyrrolo[2,3-d]pyrimidine-6-carboxamide compound of formula-3,
b) reacting the compound of formula-3 with 4-(6-amino-pyridine-3-yl)-
piperazine-1-carboxylic acid tert-butyl ester compound of formula-4 in
20 presence of a suitable base in a suitable solvent to provide tert-butyl 4-[6-[[7-
cyclopentyl-6-(dimethylcarbamoyl) pyrrolo[2)3-d]pyrimidin-2-yl]amino]-3-pyridyl]piperazine-l-carboxylate compound of formula-5,
c) treating the compound of formula-5 with a suitable acid, optionally in a
suitable solvent to provide Ribociclib compound of formula-1,
25 d) optionally, purifying the compound obtained in step-c) with a suitable solvent,
e) treating the Ribociclib compound of formula-1 obtained from step-c) or step-d) with succinic acid in a suitable solvent or mixture of solvents provides Ribociclib succinate compound of formula-la. Wherein, in step-a), the suitable coupling reagent is selected from

hydroxybenzotriazole (HOBt), l-ethyl-3-(3-dimethylaminopropyl)carbodiimide
hydrochloride (EDCHCI), benzotriazol-1-yl-oxytripyrrolidinophosphonium
hexafluorophosphate (PyBOP), Bromo-trispyrrolidino phosphonium
hexafluorophosphate (PyBrOP), 0-(benzotriazol-l-yl)-N,N,N'3N'-tetramethyluronium
5 te'trafluoroborate (TBTU), 2-(lH-Benzotriazol-l-yl)-l, 1,3,3- tetramethyluronium
hexafluorophosphate (HBTU), thionyl chloride, l-[bis(dimethylamino)methylene]-lH
1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU), l-cyano-2-
ethoxy-2-oxoethylidenaminooxy) dimethylamino-morpho|ino-carbenium
hexafluorophosphate (COMU) and tetram ethyl fluoro form am idinium
10 hexafluorophosphate (TFFH) or mixtures thereof in the presence of a base selected
from tri ethyl amine, diisopropyl ethylamine (DIPEA), N-methylmorpholine (NMM),
pyridine and the like.
In step-b), the suitable base is selected from organosilicon bases as defined above.
In step-c), the suitable acid is selected from inorganic acid such as hydrochloric acid
15 or its aqueous solution.
In step a) to e), the suitable solvent is selected from ether solvents, chloro solvents,
ester solvents, alcohol solvents, ketone solvents, polar aprotic solvents,
hydrocarbon solvents, nitrile solvents and polar solvents such as water or
mixtures thereof.
20
In the present invention, the expensive coupling reagent N,N,N',N'-
Tetramethyl-0-(l//-benzotriazol-l-yl)uronium hexafluorophosphate (HBTU) is
replaced with N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC
HC1) and hydroxybenzotriazole (HOBt) to prepare compound of formula-3. Further,
25 coupling of compound of formula-3 with 4-(6-amino-pyridin-3-yl)-piperazine-l-
carboxylic acid tert-butyl ester of formula-4 is achieved with lithium
hexamethyldisilazane (1M solution in tetrahydrofuran) to give tert-butyl4-[6-[[7-
cyclopentyl-6-(dimethylcarbamoyl)pyrTolo[2,3-d]pyrimidin-2-yl]amino]-3-
pyridyl]piperazine-l-carboxylate of formula-5 with > 80% of yield by theory, purity

by HPLC > 98.0% and the present process also avoiding highly expensive and less stable reagents like Tris(dibenzylideneacetone) dipalladium(O) (Pd2(dba)3), (+/-)-2,2'-Bis(diphenylphosphino)-l,l'-binaphthyl (BINAP) and sodium tert-butoxide.
5 In a preferred embodiment of the present invention provides an improved
process for the preparation of Ribociclib succinate compound of formula-la, comprising of:
a) Reacting 2-Crdoro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic
acid compound of formula-2 with dimethylamine in presence of N-(3-
10 Dimethylaminopropyl)-N'-ethylcarbodiimtde hydrochloride (EDC HC1),
hydroxybenzotriazole (HOBt) and N-methylmorpholine in dimethylformamide provides 2-chloro-7-cyclopentyl-N)N-dimethyl-pyrrolo [2,3-d]pyrimidine-6-carboxamide compound of formula-3,
b) reacting the compound of formula-3 with 4-(6-amino-pyridine-3-yl)-
15 piperazine-1-carboxylic acid tert-butyl ester compound of formula-4 in
presence of lithium hexamethyldisilazide (LiHMDS) in toluene provides tert-butyl 4-[6-[[7-cyclopentyl-6-(dhnethylcarbamoyl)pyrrolo[2)3-d]pyrimidin-2-yl]amino]-3-pyridyI]piperazine-l-carboxylate compound of formula-5,
c) treating the compound of formula-5 with aqueous hydrochloric acid provides
20 Ribociclib compound of formula-1,
d) purifying the compound obtained in step-c) with isopropyl alcohol or methanol,
e) treating the Ribociclib compound of formula-1 obtained from step-c) or step-d) with succinic acid in aqueous tetrahydrofuran provides Ribociclib succinate
25 compound of formula-la.
In another preferred embodiment of the present invention provides an improved process for the preparation of Ribociclib succinate compound of formula-la, comprising of:

a) Treating 2-Cfdoro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic
acid compound of formula-2 with thionyl chloride followed by reacting the
obtained compound with dimethylamine in presence of triethylamine in a
mixture of toluene and tetrahydrofuran provides 2-chloro-7-cyclopentyl-N,N-
5 dimethyl-pyrrolo[2,3-d]pyrimidine-6-carboxamide compound of formula-3,
b) reacting the compound of formula-3 with 4-(6-amino-pyridin-3-yl)-
piperazine-1-carboxylic acid tert-butyl ester compound of formula-4 in
presence of lithium hexamethyldisilazide (LiHMDS) in toluene provides tert-
butyl 4-[6-[[7-cyclopentyl-6-(dimethylcarbamoyl)pyrrolo[2,3-d]pyrimidin-2-
10 yl]amino]-3-pyridyl]piperazine-l-carboxylate compound of formula-5,
c) treating the compound of formula-5 with aqueous hydrochloric acid provides Ribociclib compound of formula-1,
d) purifying the compound obtained in step-c) with methanol,
e) treating the Ribociclib compound of formula-1 obtained from step-c) or step-
15 d) with succinic acid in aqueous tetrahydrofuran provides Ribociclib succinate
compound of formula-la.
The second aspect of the present invention is to provide crystalline Form-A of
Ribociclib succinate compound of formula-la, which is characterized by:
20 i) Its powder X-ray diffractogram having peaks at about 7.96, 8.30, 10.62, 10.93,
12.31, 14.09, 16.17, 16.45, 17.92, 19.53, 19.94, 20.64, 21.37, 24.49, 24.79, 25.12 and 25.89 ± 0.2 degrees 2-theta. ii) powdered X-ray diffraction pattern as shown in figure-1.
25 The third aspect of the present invention is to provide crystalline Form-B of
Ribociclib succinate compound of formula-la, which is characterized by:
i) Its powder X-ray diffractogram having peaks at about 10.62, 12.93, 13.09, 15.98, 18.02, 19.03, 19.72, 21.43, 21.86, and 23.19 ± 0.2 degrees 2-theta. ii) powdered X-ray diffraction pattern as shown in figure-2.

The fourth aspect of the present invention is to provide crystalline Form-C of Ribociclib succinate compound of formula-la, which is characterized by:
i) Its powder X-ray diffractogram having peaks at about 4.69, 5.00, 5.24, 8.18,
9.38, 10.03, 10.48, 12.10, 12.35, 13.17, 13.58, 13.74, 14.09, 15.78, 16.40,
5 16.83, 17.56, 18.62, 19.57, 20.37, 20.87, 21.68, 22.38, 23.46 and 28.26 ± 0.2
degrees 2-theta. ii) powdered X-ray diffraction pattern as shown in figure-3.
The fifth aspect of the present invention is to provide crystalline Form-D of 10 Ribociclib succinate compound of formula-la, which is characterized by:
i) Its powder X-ray diffractogram having peaks at about 7.68, 8.19, 8.98, 10.08,
10.64, 11.33, 12.21, 12.90, 13.91, 14.78, 15.97, 17.30, 17.89, 18.21, 19.24,
19.84, 20.89, 21.48, 21.93, 23.57, 24.23, 26.13, and 28.41 ± 0.2 degrees 2-
theta.
15 ii) powdered X-ray diffraction pattern as shown in figure-4.
The sixth aspect of the present invention is to provide crystalline Form-E of Ribociclib succinate compound of formula-la, which is characterized by:
i) Its powder X-ray diffractogram having peaks at about 4.64, 6.31, 7.51, 10.26,
20 11.34, 12.23, 13.56, 13.94, 15.71, 17.14, 19.90, 21.23, 22.48 and 24.42 ± 0.2
degrees 2-theta. ii) powdered X-ray diffraction pattern as shown in figure-5.
Further, the present invention also provides a process for the preparation of 25 crystalline Form-A, B, C, D & E of Ribociclib succinate compound of formula-la, comprising of:
a) Suspending Ribociclib compound of formula-1 in a suitable solvent,
b) heating the reaction mixture to a suitable temperature,
c) adding a solution of succinic acid in a solvent to the reaction mixture, 30 d) stirring the reaction mixture,

d) cooling the reaction mixture to a suitable temperature,
e) filtering the obtained solid to get corresponding crystalline form of Ribociclib succinate compound of formula-la.
Wherein in step-a) & c), the suitable solvent is selected from ether solvents,
5 chloro solvents, ester solvents, alcohol solvents, ketone solvents, polar aprotic solvents,
hydrocarbon solvents, nitrile solvents and polar solvents such as water or mixtures
thereof.
In step-b), the suitable temperature used is ranging from 30°C to the reflux temperature
of the solvent used;
10
The seventh aspect of the present invention is to provide crystalline Form-N of
Ribociclib succinate compound of formula-la, which is characterized by:
i) Its powder X-ray diffractogram having peaks at about 6.86, 10.05, 10.63,
12.95,15.56,16.44,17.86,18.26,20.04,20.39,20.76,21.32,21.55,22.07 and
15 25.12 ± 0.2 degrees 2-theta;
ii) powdered X-ray diffraction pattern as shown in figure-6;
iii) its DSC thermogram of crystalline Form-N of Ribociclib succinate as shown
in figure-7.
20 Further, the present invention also provides a process for the preparation of
crystalline Form-N of Ribociclib succinate compound of formula-la, comprising of:
a) Suspending Ribociclib compound of formula-1 in a suitable solvent,
b) heating the reaction mixture to a suitable temperature,
c) adding a solution of succinic acid in a solvent to the reaction mixture, 25 d) cooling the reaction mixture to a suitable temperature,
e) filtering the obtained solid to get the crystalline form-N of Ribociclib succinate compound of formula-1 a. Wherein in step-a) & c), the suitable solvent is selected from ether solvents, chloro

solvents, ester solvents, alcohol solvents, ketone solvents, polar aprotic solvents, hydrocarbon solvents, nitrile solvents and polar solvents such as water or mixtures thereof. In step-b), the suitable temperature used is ranging from 30°C to the reflux temperature 5 of the solvent used;
In a preferred embodiment of the present invention provides a process for the
preparation of crystalline Form-N of Ribociclib succinate compound of formula-la,
comprising of:
10 a) Suspending Ribociclib compound of formula-1 in tetrahydrofuran,
b) heating the reaction mixture to 60-65°C,
c) adding an aqueous tetrahydrofuran solution of succinic acid to the solution obtained in step-(b),
d) cooling the reaction mixture to 25-35°C,
15 e) filtering the obtained solid to get the crystalline form-N of Ribociclib
succinate compound of formula-la.
The crystalline forms A, B, C, D, E & N of Ribociclib succinate of the present invention are useful for the preparation of pharmaceutical compositions.
20
The process for the preparation of Ribociclib succinate compound of formula-la is schematically represented in Scheme-I as below:
25
Scheme-I:

PXRD method of analysis:
PXRD analysis of the crystalline forms of Ribociclib succinate compound of formula-la were carried out using Panlytical Expert. Pro DY3248 X-ray powder diffractometer using Cu-Ka radiation of 10 wavelength 1.5406 A° and at continuous scan speed of 0.03°/min.
DSC Method of Analysis:
Differential scanning calorimetric (DSC) analysis was performed with TA / 2500 Discovery. Samples of about 2 to 3 milligrams held in a Tzero Aluminum Hermetic closed pan were analyzed at a heating rate of 10°C per minute.
The best mode of carrying out the present invention was illustrated by the below mentioned examples. These examples are provides as illustration only and hence should not be construed as limitation of the scope of the invention.

Examples:
Exampc-1: Preparation of 2-chloro-7-cyclopentyl-N,N-dimethyl-pyrrolo(2,3-
d]pyrimidine-6-carboxamide (Formula-3)
Methylene chloride (1000 mL) and 2-Chloro-7-cyclopentyl-7H-pyrrolo[2]3-5 d]pyrimidine-6-carboxylic acid (50.0g, 0.188 moles) were charged into 2L 4N RB flask under nitrogen atmosphere, and stir of 5- lOmin to get brown colored suspension. Reaction mass was cooled to 0±2°C. HOBt (28.0g, 0.207 moles), EDC.HC1 (39.7gJ 0.207 moles) were charged into the reaction mass and stir for 5-10 min at 0 ± 2°C. Dimethylamine 2M solution in ethanol (139.0 mL, 0.282 moles) added dropwise to the
10 reaction mass through addition funnel by maintaining mass temperature at 0 ±2°C. Then reaction mass was stirred for 5-10 min at 0 ± 2°C. Reaction mass temperature was raised to 30±5°C and stirred for 7-8h.
After completion of reaction (by TLC) solvent was distilled off under vacuum on rotavapor at 40°C to yield brown colored oily crude. The resulting crude was
15 dissolved in ethyl acetate (1500.0 mL) and stirred for 5-10min at 25-35°C to get brown colored clear solution. DM water (500.0 mL) was charged to the reaction mass and stirred for 5-1 Omin. Layers were separated, organic layer was washed with aq.potassium carbonate solution (lOg of potassium carbonate was dissolved in 500.0 mL of DM water). Followed by DM water (500.0 mL) and layers were separated.
20 Organic layer was dried over sodium sulphate and filtered. Solvent from the filtrate was distilled off completely under vacuum at 50°C on rotavapor to obtain brown colored oily crude. n-Heptane (100 mL) was charged to the oily crude and again solvent was distilled off. The resulting oily crude was leached with n-heptane (250.0 mL) at 30 ± 5°C for lh. Product was filtered under suction with the help of n-heptane (50 mL).
25 The wet product was dried in hot air oven at 45-50°C for 6h to afford title compound. Wt. of the product 43.0g (78% by theory). Purity by HPLC > 98.0%. H1 NMR (DMSO): 8 8.967 (S, 1 H), 6.801 (S, 1 H), 4.803 (m, 1 H), 3.007-3.051-(S, 6 H), 2.182-2.251 (m, 2H), 1.964-2.063 (m, 4 H), 1.891-1.945 (m, 2 H), 1.607-1.670 (m, 2H),; Mass m/z (M+l): 293.1

Example-2: Preparation of tert-butyl 4-[6-|I7-cyclopentyl-6-(dimethylcarbamoyl)
pyrroIo[2,3-dlpyrimidin-2-yl]amino]-3-pyridyllpipera2ine-l-carboxylate
(Formula-5)
Toluene (432.0 mL) and 4-(6-amino-pyridine-3-yl)-piperazine-l-carboxylic 5 acid tert-butyl ester (34.3g, 0.123 moles) were charged into 2L 4N RB flask under nitrogen atmosphere at 30±5°C and stirred for 5-10 min to get brown colored suspension. Reaction mass was cooled to 0±5°C. Lithium hexamethyldisilazane 1M solution in THF (259.0 mL, 0.258 moles) was added dropwise to the reaction mass through addition funnel by maintaining the reaction mass temperature at 0 ±5°C. And
10 stirred the reaction mass for 10-15 min at 0 ± 5°Cto get clear brown colored solution. Add the solution of 2-chloro-7-cyclopentyl-N,N-dimethyl-pyiTolo[2,3-d]pyrirnidine-6-carboxamide (36.Og, 0.123 moles) in 324.0 mL of toluene dropwise to the reaction mass through addition funnel at 0 ±5°C. Reaction mass temperature was raised to 25-35°C and stirred for lh for reaction completion.
15 After completion of reaction (by TLC), solvent was distilled off on rotavapor under vacuum at 55-60°C to get the brown colored solid. DM water (360.0 mL) and aq. sodium bicarbonate solution (36.Og of sodium bicarbonate was dissolved in 720.0 mL of DM water) were added to the above solid and stirred for 10-15 min. Then methylene chloride (720 mL) was charged to the above solution and stirred for 5-10min. Layers
20 were separated. Organic layer washed with DM water (720 mL) and layers Separated. Solvent was distilled off from organic layer completely under vacuum at 45-50°C on rotavapor to obtain brown colored solid. The solid was leached with methanol (180. mL) at 30 ± 5°C to afford title compound as pale brown colour solid. Weight of the product: 57.0g (86.6% by theory). Purity by HPLC > 98.0%.
25 H1 NMR (DMSO-d6): 5 9.412 (S, 1 H), 8.167-8.190 (d, 2 H), 8.02-8.03 (d, 1 H),
7.449-7.479 (dd, 1 H), 6.603 (S, 1 H), 4.690-4.778 (m, 1 H), 3.472-3.484 (d, 4H), . -3.062-3.073 (d, 10H), 2.413-2.465 (m, 12 H), 1.92-1.991 (m, 4 H), 1.427-1.65 (m, 10H); Mass m/z(M+l): 535.25

ExampIe-3: Preparation of Ribociclib (Formula-1).
1,4-Dioxane (300.0 mL) and ten-butyl 4-[6-[[7-cyclopentyl-6-(dimethylcarbamoyl) pyrrolo[2,3-d]pyrimidm-2-yl]ammo]-3-pyridyl]piperazine-l-carboxylate(30.0g, 0.056 moles) were charged into 1L 4N RB flask under nitrogen 5 atmosphere at 30±5°C and stirred for 5-10 min. Dilute aq.hydrochloric acid (96.8 mL, 0.56 moles, prepared by diluting 48.4 ml of Conc.HCl with 48.4ml of DM water) was added as dropwise to the reaction mass through addition funnel at 30 ±5°C. Reaction mass was stirred for 6-7h for reaction completion. After reaction completion (by TLC), reaction mass was diluted with DM water (1200
10 mL) and stirred for 5-10min. Reaction mass was washed three times with ethyl acetate (300 mLx3) and layers were separated. Aqueous layer pH was adjusted to 10-11 using aq.NaOH (40.0g of NaOH was dissolved in 800.0 mL of DM water) and stirred the reaction mass for lh at 30 ±5°C. Product was filtered under suction with the help of DM water (60 mL) and wet product was slurry washed with IPA (30 mL). Product was
15 recrystallized from isopropyl alcohol and dried in hot air oven for 6h at 70-75°C. Weight of the product: 19.2g (78.8% by theory). Purity by HPLC > 99.0%. H1 NMR (DMSO-d6): 5 9.310 (S, 1 H), 8.757 (S, 1 H), 8.127-8.150 (d, 1 H), 7.974-7.981 (d, 1 H), 6.596 (S, 1 H), 4.685-4.773 (m, 1 H), 3.008-3.050 (m, 10H), 2.835-2.859 (m, 4H), 2.330-2.461 (m, 4 H), 1.977-1.990 (m, 4 H), 1.631-1.644 (m, 2H),;
20 Mass m/z (M+l): 435.24
Example-4: Preparation of Polymorphic Form-A of Ribociclib succinate (Formula-1 a)
Tetra hydro furan (120 mL) and Ribociclib (3.0g, 0.0069 moles) were charged 25 into 250 mL 4 neck round bottomed flask at 30±5°C and stirred for 5-10 min. to get cream colored suspension. Reaction mass was heated to 65-70°C and stirred for 15 min. to get clear solution. The solution of succinic acid (0.85g, 0.0072moles) in tetrahydrofiiran (60 mL) was added to the above reaction mass dropwise through addition funnel at 65-70°C. After addition of succinic acid solution, pale yellow

coloured suspension was formed in the reaction mass and was stirred for 1 h. Then the reaction mass was cooled to 25-35°C and stirred for lh. Product was filtered off under suction. Product was dried in vacuum oven at 65-70°C to afford title compound as cream coloured solid. Weight of the product: 3.7g (97.1% by theory) as cream coloured 5 solid. Purity by HPLC > 99.0%.
The obtained crystalline compound is characterized by PXRD as illustrated in figure-1.
ExampIe-5: Preparation of Polymorphic Form-B of Ribociclib succinate 10 (Formula-la)
Methanol (90 mL) and Ribociclib (3.0g, 0.0069 moles) were charged into 250 mL 4 necked round bottomed flask and stirred at 30±5°C for 5-10 min. Reaction mass was heated to 65-70°C and stirred to get clear solution. Then the solution of succinic acid (0.85g, 0.0072 moles) in methanol (30 mL) was added to the reaction mass
15 dropwise through addition funnel at 65-70°C and stirred for lh. Reaction mass was cream coloured hazy solution. Then reaction mass was cooled to 25-35°C and stirred for lh. Product was filtered under suction and dried in vacuum oven at 65-70°C to afford title compound as cream coloured solid. Weight of the product: 3.2g (84.0% by theory). Purity by HPLC > 99.0%.
20 The obtained crystalline compound is characterized by PXRD as illustrated in
figure-2.
ExampIe-6: Preparation of Polymorphic Form-C of Ribociclib succinate (Formula-la)
25 Ethanol (135 mL) and Ribociclib (3.0g, 0.0069 moles) were charged into 250
ml 4 necked round bottomed flask and stirred at 30±5°C for 5-10 min. Reaction mass was heated to 70-75°C to get clear solution. Then the solution of Succinic acid (0.85g, 0.0072moles) in ethanol (15 mL) dissolved at 70-75°C was added dropwise through addition funnel to the above solution at 70-75°C and then stirred for lh. Reaction mass

was pale cream coloured hazy solution. Reaction mass was cooled to 25-35°C and
stirred for lh 30min. Product was filtered from the resulting suspension under suction
and dried in vacuum oven at 65-70°C to afford title compound as cream coloured solid.
Weight of the product: 3.0g (78.7% by theory). Purity by HPLC > 99.0%.
5 The obtained crystalline compound is characterized by PXRD as illustrated in
figure-3.
Example-7: Preparation of Polymorphic Form-D of Ribociclib succinate (Formula-la)
10 n-Butanol (75 mL) and Ribociclib (3.0g, 0.0069 moles) were charged in to 250
mL 4 neck round bottomed flask and stirred at 30±5°C for 5-10 min. Reaction mass was heated to 70-75°C and stirred for 20 min and filtered to get clear solution. The filtrate was transferred into 250 mL 4 neck round bottomed flask and heated to 70-75°C. Then the solution of succinic acid (0.85g, 0.0072 moles) in n-Butanol (15 mL)
15 dissolved at 70-75°C was added dropwise to the reaction mass at 70-75°C and stirred for lh. Reaction mass was cooled to 25-35°C and stirred for lh. Product was filtered off under suction and dried in vacuum oven at 65-70°C to get the title compound as cream coloured solid. Weight of the product: 3.0g (78.7% by theory). Purity by HPLC > 99.0%.
20 The obtained crystalline compound is characterized by PXRD as illustrated in
figure-4.
ExampIc-8: Preparation of Polymorphic Form-E of Ribociclib succinate (Formula-la)
25 Methylene chloride (40 mL) and Ribociclib (2.0g, 0.0046 moles) were charged
in to 250 mL 4 neck round bottomed flask at 30±5°C and stirred for 5-10 min. Reaction mass was heated to 35-40°C and stirred for 30 min. to get clear solution. The succinic acid (0.57g, 0.0048 moles) solution in tetrahydrofuran (10 mL) was added dropwise to the reaction mass at 35-40°C. Reaction mass was turned to cream coloured suspension
30 and was stirred for lh. Reaction mass was cooled to 25-35°C and stirred for lh. Product

was filtered off under suction and dried in vacuum oven at 65-70°C to yield the title
compound as cream coloured solid. Weight of the product: 2.2g (86.6% by theory). j
Purity by HPLC > 99.0%.
The obtained crystalline compound is characterized by PXRD as illustrated in 5 figure-5.
Exampe-9: Preparation of 2-chloro-7-cycIopenryl-N,N-dimethyl-pyrrolo[2,3-dl pyrimidine-6-carboxamide ((Formula-3)
N,N-Dimethylformamide (150 mL) and 2-Chloro-7-cyclopentyl-7H-
10 pyirolo[2,3-d]pyrimidine-6-carboxylic acid (50.0g, 0.188 moles) were charged into 2L 4N RB flask under CaCh guard tube condition, and stirred of 5-10 min to get cream colored suspension. Reaction mass was cooled to 0-5°C. HOBt (28.Og, 0.207 moles), EDC.HC1 (57.7g, 0.301 moles) were charged into the reaction mass and stirred for 5.-10 min at 0-5°C. Dimethylamine 2M solution in THF (141.0 mL, 0.282 moles) was
15 added dropwise to the above reaction mass by maintaining the mass temperature at 0-5°C. Then reaction mass was stirred for 5-10 min at 0 -5°C. N-Methylmorpholine (57. lg, 0.564 moles) was added dropwise to the reaction mass by maintaining mass temperature at 0 -5°C and stirred for 5-10 min at 0 -5°C. Reaction mass temperature was raised to 25-3 5°C and stirred for 12-15h.
20 After completion of reaction (by HPLC), added lOOO.OmL chilled water (5-10°C) and stirred for 10-15min. Aq.sodium bicarbonate solution (50g of sodium bicarbonate was dissolved in 1000.0 mL DM water) was added to the reaction mass and stirred for lh to get cream colored suspension. Product was filtered under suction with the help of DM water (500 mL). The wet product leached from DM water (500.0 mL). The wet
25 product was dried in hot air oven at 60-65°C for 6h to afford title compound. Wt. of the product 43.Og (78.2% by theory). Purity by HPLC > 99.0%.
Exampe-10: Preparation of 2-chloro-7-cyclopentyl-N,N-dimethyl-pyrrolo[2,3-d)pyrimidine-6-carboxamide (Formula-3)

Toluene (500 mL) and 2-Chloro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic acid (100.Og, 0.377 moles) were charged into 2L 4N RB flask under CaCb guard tube condition, and stirred of 5-10 min to get cream colored suspension. Added N,N-dimethylformamide (10.0 mL) and stirred for 5-10 min. Charged thionyl 5 chloride (67.2g, 0.566 moles) to the reaction mass and stir for 5-10min. at 25-35°C to get pale brown colored suspension. Reaction mass was heated to 75-80°C and stirred for 3-4h. After completion of reaction (by HPLC), cooled to 0-5°C to become brown colored suspension. Mixture of 2M solution of dimethylamine in THF (470.0 mL, 0.942 moles) and triethylamine (122.Og, 1.20 moles) added dropwise to the reaction
10 mass through addition funnel by maintaining the mass temperature at 0-10°C and then stirred for 5-10 min. Reaction mass temperature was raised to 25-35°C and stirred for l-2h. After completion of reaction (by HPLC) solvent was distilled off under vacuum on rotavapor at 60-65°C to yield brown colored crude. The resulting crude was dispersed in DM water (1000.0 mL) and stirred for lh at 25-35°C to get cream colored
15 suspension. Product was filtered under suction with the help of DM water (500 mL). The wet product was dried in hot air oven at 60-65°C for 6h to afford the title compound. Wt. of the product 106.0g (96.4% by theory). Purity.by HPLC > 99.0%.
Example-ll: Preparation of tert-buryl 4-[6-[[7-cyclopentyl-6-(dimethyl 20 carbamoyl)pyrroIo[2,3-d]pyrimidin-2-yl]amino]-3-pyridyl)piperazine-l-carboxylate (FormuIa-5)
Toluene (300.0 mL) and 4-(6-amino-pyridine-3-yl)-piperazine-l-carboxylic acid tert-butyl ester (95.3g, 0.342 moles) were charged into 2L 4N RB flask under nitrogen atmosphere at 25-35°C and stirred for 5-10 min to get brown colored 25 suspension. Reaction mass was cooled'to 0-5°C. Lithium hexamethyldisilazane 1M solution in THF (710.0 mL, 0.718 moles) was added dropwise to the reaction mass through addition funnel by maintaining the reaction mass temperature at 0-10°C then the reaction mass was stirred for 10-15 min at 0-5°C to get clear brown colored solution. The solution of 2-chloro-7-cyclopentyl-N,N-dimethyl-pyrrolo[2,3-

d]pyrimidine-6-carboxamide (100.Og, 0.342 moles) in 300.0 mL of toluene was added dropwise to the reaction mass through addition funnel at 0-5°C. After completion of addition reaction mass temperature was raised to 25-35°C and stirred for lh. After completion of reaction (by HPLC), reaction mass quenched with DM water (100 5 mL) by maintaining the reaction mass temperature at 25-35°C and stirred for 5-10 min. to get brown colored suspension. Solvent was distilled off on rotavapor under vacuum at 60-65°C to get the brown colored solid. The resulting solid was leached with methanol (800 mL) at 25-35°C followed by DM water (1000 mL). Solid was filtered and dried in hot air oven at 60-65°C for 6h to afford title compound as pale brown color 10 solid. Weight of the product: 142.0g (77.6% by theory). Purity by HPLC > 99.0%.
Example-12: Preparation of Ribociclib (Formula-1)
DM water (200.0 mL) and tert-butyl 4-[6-[[7-cyclopentyl-6-(dimethyl carbamoyl)pyrrolo[233-d]pyrimidin-2-yl]amino]-3-pyridyl]piperazine-l-carboxylate
15 (40.0g, 0.075 moles) were charged into 1L 4N RB flask at 30±5°C and stirred for 5-10 min. to get cream colored suspension. Reaction mass was heated to 40-45°C and diluted aq.hydrochloric acid (199.0 mL, 0.561 moles, prepared by diluting 49.0 mL of Cone, hydrochloric acid with 150 mL of DM water) was added dropwise to the above reaction mass and stirred for about lh to get pale brown colored clear solution.
20 Resulting clear solution was further stirred for l-2h for reaction completion.
After reaction completion (by HPLC), reaction mass was diluted with DM water (80 mL) and stirred for 5-10min. Reaction mass was washed with ethyl acetate (200 mL x 2) and layers were separated. Aqueous layer was basified using aq.sodium hydroxide solution (45.Og of sodium hydroxide was dissolved in 900.0 mL of DM water) and
25 stirred the resulting cream colored suspension for lh at 25-35°C. Product was filtered under suction with the help of DM water (200 mL). Wet product was leached from DM water (400 mL) followed by methanol (200 mL) and product was filtered and dried in hot air oven for 6h at 70-75°C. Weight of the product: 29.6g (91.0% by theory). Purity byHPLC>99.0%.
:NT OFFICE CHENNAI 2 3 /33 1 / 2 Q 1 9 12=44

Example-13: Preparation of Polymorphic Form-N of Ribociclib succinate
(Formula-la)
Tetrahydrofiiran (280mL) and Ribociclib (7.0g, 0.0161 moles) were charged into 500ml 4N round bottomed flask at 30±5°C and stirred for 5-10 min. to get cream 5 colored suspension. Reaction mass was heated to 60-65°C and stirred for 15 min. to get clear solution. After clear solution, activated carbon (0.7g) was charged and stirred for 30min. Reaction mass was filtered under suction. Filtrate was transferred into fresh 500ml 4N round bottomed flask and heated to 60-65°C. The aq. tetrahydrofiiran solution of succinic acid (prepared by dissolving succinic acid 1.9g, 0.0161 moles in
10 the solvent mixture of tetrahydrofiiran (19.6 ml) and water (3.9 ml)) was added drop wise to the above solution of Ribociclib at 60-65°C. Reaction mass was cooled to 30±5°C and stirred for lh to get off-white to cream colored suspension. Reaction mass was filtered under suction under nitrogen atmosphere and suck dried for 30-45min. Product was further dried in vacuum oven for 24h at 50-55°C to afford title compound.
15 Weight of the product: 7.9g (88.4% by theory). Purity by HPLC: 99.86%. Mass m/z (M+l): 435.14
H1NMR(DMSO-d6):5 9.344(S, 1 H), 8.763 (S, 1 H), 8.146-8.169 (d, 1 H), 6 8.001-8.008 (d, 1 H), 7.420-7.450 (dd, 1 H), 6.600 (S, 1H), 4.689-4.777 (m, 1 H), 3.103-3.128 (m, 4 H), 3.056 (m, 5 H), 2.963-2.988 (m, 4 H), 2.410-2.463 (m, 2H), 2.307(s, 2H),
20 1.974-1.980(m, 4H) 1.634-1.663 (m, 2 H).
The obtained crystalline compound is characterized by PXRD as illustrated in figure-6 and its DSC thermogram as illustrated in figure-7.

We Claim:
1. An improved process for the preparation of Ribociclib succinate compound of
formula-la, comprising of:
a) Treating 2-Chloro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic acid
5 compound of formula-2
dimethyfamine in presence of a base in a suitable solvent provides 2-chloro-7-cyclopentyl-N,N-dimethyl-pyrrolo[2,3-d]pyrimidine-6-carboxamide compound of formula-3,
_ n
rormula-3 b) reacting the compound of formula-3 with 4-(6-amino-pyridin-3-yl)-piperazine-l-carboxylic acid tert-butyl ester compound of formula-4
in presence of a suitable organosilicon base in a suitable solvent to provide tert-butyl 4-[6-[[7-cyclopentyl-6-(dimethylcarbamoyl)pyrrolo[233-d]pyrimidin-2-yl]amino]-3-pyridyl]piperazine-l-carboxylate compound of formula-5,

Formula-5
c) treating the compound of formula-5 with aqueous hydrochloric acid, optionally in a
suitable solvent to provide Ribociclib compound of formula-1,
. 9
5 HiO
Formula-1
d) optionally, purifying the compound obtained in step-c) with a suitable solvent,
e) treating the Ribociclib compound of formula-1 obtained from step-c) or step-d) with succinic acid in a suitable solvent or mixture of solvents provides Ribociclib ■
10 succinate compound of formula-la.
2. The process as claimed in claim-1, wherein,
In step-a) the suitable base is selected from triethylamine, dimethylamine,
diethylamine, diisopropylamine, diisopropylethylamine and diisobutylamine. 15 In step-b) the suitable organosilicon base used is selected from lithium
hexamethyldisilazide (LiHMDS), sodium hexamethyldisilazide (NaHMDS),
potassium hexamethyldisilazide (KHMDS) or mixtures thereof. In step a) to e), the suitable solvent is selected from ether solvents, chloro solvents,
ester solvents, alcohol solvents, ketone solvents, polar aprotic solvents,
20 hydrocarbon solvents, nitrile solvents and polar solvents such as water or
mixtures thereof.

3. The process as claimed in claim-1, comprising of:
a) Treating 2-Chloro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic acid
compound of formula-2 with thionyl chloride followed by reacting the obtained
compound with dimethylamine in presence of triethylamine in a mixture of toluene
5 and tetrahydrofuran provides 2-chloro-7-cyclopentyl-N,N-dimethyl-pyrrolo[2,3-
d]pyrimidine-6-carboxamide compound of formula-3,
b) reacting the compound of formula-3 with 4-(6-amino-pyridin-3-yl)-piperazine-l-
carboxylic acid tert-butyl ester compound of formula-4 in presence of lithium
hexamethyldisilaztde (LiHMDS) in toluene provides tert-butyl 4-[6-[[7-
10 cyclopentyl-6-(dimethylcarbamoyl)pyrrolo[2,3-d]pyrimidin-2-yl]amino]-3-
pyridyl]piperazine-l-carboxylate compound of formula-5,
c) treating the compound of formula-5 with aqueous hydrochloric acid provides Ribociclib compound of formula-1,
d) purifying the compound obtained in step-c) with methanol,
15 e) treating the Ribociclib compound of formula-1 obtained from step-c) or step-d) with succinic acid in aqueous tetrahydrofuran provides Ribociclib succinate compound of formula-la.
20 4. The process as claimed in claim-1, wherein, the process for the preparation of 2-chloro-7-cyclopentyl-N,N-dimethyl-pyrrolo[2,3-d]pyrimidine-6-carboxamide compound of formula-3, comprising of treating 2-Chloro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic acid compound of formula-2 with thionyl chloride followed by reacting the obtained compound with dimethylamine in
25 presence of triethylamine in a mixture of toluene and tetrahydrofuran provides 2-
chloro-7-cyclopentyl-N,N-dimethyl-pyrrolo[253-d]pyrimidine-6-carboxamide compound of formula-3.
JO 5. The process as claimed in claim-1, wherein, the process for the preparation of tert-butyl 4-[6-[[7-cyclopentyl-6-(dimethylcarbamoyl)pyrrolo[2,3-d]pyrimidin-2-yl]

amino]-3-pyridyl]piperazine-l-carboxylate compound of formula-5, comprising of
reacting the compound of formula-3 with 4-(6-amino-pyridin-3-yl)-piperazine-l-
carboxylic acid tert-butyl ester compound of formula-4 in presence of lithium
hexamethyldisilazide (LiHMDS) in toluene provides tert-butyl 4-[6-[[7-
5 cyclopentyl-6-(dimethylcarbamoyl)pyrrolo[2,3-d]pyrimidin-2-yl]amino]-3-
pyridyl]piperazine-l-carboxylate compound of formula-5.
6. The process as claimed in claim-1, wherein, the process for the preparation of
Ribociclib compound of formula-1 comprising of treating the compound of formula-
10 5 with aqueous hydrochloric acid provides Ribociclib compound of formula-1.
7. A crystalline Form-N of Ribociclib succinate compound of formula-la, which is
characterized by:
i) Its powder X-ray diffractogram having peaks at about 6.86, 10.05, 10.63, 12.95,
15 15.56,16.44, 17.86,18.26,20.04,20.39,20.76,21.32,21.55,22.07 and25.12±0.2
degrees 2-theta. ii) powdered X-ray diffraction pattern as shown in figure-6.
8. The process for preparing the crystalline Form-N of Ribociclib succinate compound
20 of formula-la, comprising the steps of:
a) Suspending Ribociclib compound of formula-1 in a suitable solvent,
b) heating the reaction mixture to a suitable temperature,
c) adding a solution of succinic acid in a solvent to the reaction mixture,
d) cooling the reaction mixture to a suitable temperature,
25 e) filtering the obtained solid to get the crystalline form-N of Ribociclib succinate compound of formula-la.
9. The process as claimed in claim-8, wherein;
In step-a) & c) the solvent used is selected from ether solvents, chloro solvents, ester

solvents, alcohol solvents, ketone solvents, polar aprotic solvents, hydrocarbon solvents, nitrile solvents and polar solvents such as water or mixtures thereof. In step-b), the suitable temperature used is ranging from 30°C to the reflux temperature of the solvent used.
5
10. The crystalline Form-N of Ribociclib succinate compound of formula-la as
claimed in claim-8, comprising the steps of:
a) Suspending Ribociclib compound of formula-1 in tetrahydrofuran,
b) heating the reaction mixture to 60-65°C,
10 c) adding an aqueous tetrahydrofuran solution of succinic acid to the solution obtained in step-(b),
d) cooling the reaction mixture to 25-35°C,
e) filtering the obtained solid to get the crystalline form-N of Ribociclib succinate compound of formula-la.
1 C